Patients having H. pylori-positive chronic gastritis with/without small erosions or peptic ulcer scars will be recruited. Before treatment, H. pylori infection status will be examined by endoscopy with biopsy or 13C-urea breath test (13C-UBT). All patients will receive 13C-UBT before treatment, at the end of 2 week's treatment and 4 weeks after termination of treatment. A computed generated random numbers sequence will be blocked (2:1; block sizes of six) into two groups, say A and B.